In a related art, a surge protecting device is always provided to an IC to prevent the IC from being damaged by a surge voltage. The surge voltage is generated by a surge signal transmitted from a web line or a circuit line, which always has a lower frequency than an ESD (ElectroStatic Discharge) signal. Therefore, a traditional ESD protecting device can not protect the IC from being damaged by the surge voltage.
FIG. 1 is a circuit diagram illustrating a related art surge protecting mechanism. As shown in FIG. 1, an IC (integrated circuit) 101 is provided on a board 100. A surge protecting device 105 is provided in a hybrid circuit near the IC 101. The hybrid circuit comprises a transformer 103, the surge protecting device 105, a resistance network comprising resistance devices Ra, Rb, Rc, Rd,Re, Rf, a transmitter 107 and a receiver 109. The transmitter 107 and a receiver 109 are provided inside the IC 101 (but also can outside the IC) and other devices for the hybrid circuit are outside the IC 101. If a surge voltage Vsr occurs, it is reduced by the primary side and the secondary side of the transformer 103, and then released by the surge protecting device 105. The surge protecting device 105 can comprises various kinds of structures. For example, it can comprise zener diodes D1, D2, D3 and D4 as shown in FIG. 1.
However, as shown in FIG. 1, the surge protecting device 105 is provided on the board 100, thus the space for the board 100 is occupied and the cost increases.